The type of herbicidal formulation plays an important role in the efficacy of weed control. Various types of herbicidal formulations aim to boost efficacy of the herbicide such that the active ingredient is delivered to the weed with maximum efficacy, minimum waste and prolonged residual effect.
A combination of two active ingredients sometimes leads to incompatibility. It is not uncommon for physical and biological incompatibility to occur, for example insufficient stability of a joint formulation, decomposition of an active ingredient or antagonism of the active ingredients. Incompatibility can lead to the mixture forming a precipitate, or a gel or flakes that settle down rendering the herbicidal mixture and the container useless. This will also result in inefficient spraying of the pesticide, resulting in poor efficacy. It is therefore important for formulators to prepare stable formulations that allow for two incompatible actives to be combined in a single formulation, giving a favourable active profile, high stability and in some cases enhanced synergy, thus permitting reduced rate of application as compared with the individual application of the active compounds. There is therefore a need in the art for a formulation which is stable especially when two incompatible active compounds are combined providing a broader spectrum of control while reducing rate of application.
Herbicidal combinations are used for effective and economical weed control. These combinations offer advantages like broad spectrum of herbicidal action, synergistic effect, prevention of degradation of one herbicide due to the presence of the second herbicide and reduction of dosages of the herbicides.
These herbicidal combinations may be prepared by tank mixing the individual herbicides at the desired rates just before application. However, regulating the rates of individual herbicides in the tank-mixed combinations is a problem for many farmers, who often tend to overdose the herbicides leading to undesired effects in the field crops. Therefore, it is more preferable to prepare formulations comprising the herbicidal combinations at the time of manufacturing. These formulations and their preparation suffer from the complication of mutual degradation and incompatibility of the herbicides when presented and stored in the same formulation for an extended period of time. It is often a challenge for a skilled formulator to prepare a stable composition comprising a combination of two or more active ingredients.
ZC formulations are a combination of capsule suspension and suspension concentrate such that the formulation contains a stable aqueous suspension of microcapsules and solid fine particles (in an aqueous phase), each of which contains at least one active ingredient.
Pendimethalin is a dinitroaniline herbicide. It is a selective herbicide which controls certain broadleaf weeds and grassy weed species in crop and non-crop areas. It is applied to soil at pre-plant, pre-emergence, and post-emergence stages with ground and aerial equipment. It is a low melting active with negligible vapour pressure that is notorious for its problem of staining plants as well as the every other commodity it comes in contact with.
The application PCT/IB2011/002280 discloses a capsule suspension comprising microcapsules in an organic phase and an aqueous phase optionally comprising a second herbicide. The microcapsules encapsulate pendimethalin. The aqueous phase includes an alkali or alkaline earth metal salt of an organic acid.
This application describes that the second herbicide may be either co-microencapsulated with pendimethalin or may be unencapsulated or may be microencapsulated separately and admixed with microencapsulated pendimethalin. The second herbicide is predominantly clomazone or a volatile herbicide such as 2,4-D esters, MCPA esters, triclopyr or picloram. This application does not envisage any further combination partner for encapsulated pendimethalin.
Pendimethalin is known to be incompatible with several classes of herbicides due to its physical characteristics that lead to unstable formulations. The other known water based formulations are also not known to work well for pendimethalin. There is therefore a need in the art for stable, compatible water based formulations of pendimethalin that—                a. Deliver stain free pendimethalin formulations with a co-active herbicide.        b. Provide a physically stable formulation of pendimethalin with a co-active herbicide.        c. Provide a formulation of pendimethalin with a co-active that has prolonged herbicidal effect.        d. Provide water based environmentally friendly formulation of pendimethalin with a co-active herbicide.        e. Provide a formulation of pendimethalin that overcomes the incompatibility with other active ingredients.        
The present invention therefore aims to solve the problem of incompatibility and stability with the use of ZC formulations, specifically for actives such as pendimethalin when combined with herbicides which are otherwise known to be incompatible with pendimethalin.
Embodiment of the present invention can ameliorate one or more of the above mentioned problems: